In order to improve the rigidity of a vehicle body of an automobile, there is known a vehicle body structure in which a floor member is installed on a floor panel constituting a floor of an interior of a vehicle to extend in the longitudinal direction of the vehicle and the floor panel and the floor member form a closed cross-section. In the technique disclosed in PTL 1, a recess (a groove) is formed in the floor panel to extend in the longitudinal direction, and a floor member is accommodated inside the groove to suppress a step portion from being formed on the floor of the interior of a vehicle. A rear end of the floor member is fixed to a cross member extending in the width direction of the vehicle for the reinforcement thereof.